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TDS meter

Know what you are measuring -TDS meter

TDS meter

This past week I listened to a broadcast on the radio where a water expert was interviewed. Although I have great appreciation for this expert, my toes began to curl at some of the comments he made about measuring with a TDS meter.

TDS stands for Total Dissolved Solids, or total dissolved solids in a liquid. These meters are used by many a water filter provider to display the purity of the filtered water.

How does a TDS meter work?

A TDS meter is actually a conductivity meter. It works by applying a voltage between two or more electrodes. Positively charged ions (these include minerals and trace elements such as calcium, magnesium, sodium, zinc, iron) will move to the negatively charged electrode. Negatively charged ions (e.g., chloride, sulfate, sulfite, fluoride) will move to the positively charged electrode.

As these ions are charged and move, they form an electric current. The TDS meter measures how much current flows between the electrodes. This makes it possible to determine how many ions are in a solution
. The result is displayed in ppm (parts per million).

If you were to measure only pure water (H2O) the meter would read 0. I hear you thinking: so if a TDS meter reads more than 0 then there are pollutants in it.

No is the answer to this. It only indicates that it contains other substances besides water.

I made a video where I add acetone, benzene and brake cleaner to demineralized water and the TDS gives a very low value. Only when adding minerals does the TDS value increase.

Pure water (H2O) does not occur in nature. Nor would it be good for nature because without minerals and trace elements, flora and fauna could not live.

What does a TDS meter actually measure?

It is important to know what such meters do NOT actually test. This is because they only measure mobile charged ions. They cannot detect neutral (uncharged) compounds. This includes compounds such as sugar, alcohol, many organic substances (including chemicals, drugs, hormones, many pesticides and their residues) and non-ionized forms of silica, ammonia and carbon dioxide. These meters also do not measure macroscopic particles because they are too large to move in the applied electric fields. So if you see "rusty" water from iron oxide particles, it will not be measured. Bacteria, viruses and micro plastics are also not measured.

Substances such as PF(O)AS used in the GenX process, among others, Chromium-6 and even lead cannot be measured with a TDS meter either because these substances occur in parts per billion or even smaller.

So the designation "total dissolved solids" is a misnomer. It is better to say that you have measured the total amount of charged ions.

If a TDS meter reads 8, at least you know that almost all minerals and trace elements have been removed from the water. However, the water may be heavily contaminated with drugs, pesticides, GenX, bacteria, micro plastics, chemicals, etc.

How can the quality of filtered water be determined?

So with a TDS meter you can NOT test the quality of filtered water. That can only be tested at a laboratory. Ask a water filter supplier for test reports. Don't be fooled if you get comments such as, "Activated carbon is known to filter out these, these, these and these substances. Our filter has carbon so it removes these substances as well.". If it were that easy then the drinking water companies would also have removed all those substances from the water. It is the combination of filters needed to filter extra well and the time the water is in contact with the filter materials. With most filters, the water passes through the filter too quickly. Aqualine systems only filter an average of 1.5 liters per hour. So the water is in contact with the filter materials for a longer time.

Our Aqualine filters are proven to remove the PF(O)AS from the water used in the GenX process. In addition, we remove a large number of other substances from the water.

Our Aqualine filters have a higher TDS and that's because we add minerals to the filtered water. If you choose the alkaline version, the included pH ring also releases some additional minerals and magnesium to raise the pH of the water to slightly alkaline water.

Some providers indicate that we should only drink H2O. So this is water in its purest form. So this is water that is also free of minerals and trace elements. For as long as humanity has existed we have been drinking water from springs and rivers. Depending on the soil conditions, this water is rich in all kinds of different minerals and trace elements. Flowers and plants cannot grow without minerals.

That we want to purify the water from pollution I understand, but why do we want to filter the natural elements out of the water?

Aqualine water filter systems mimic nature. We remove the contamination as much as possible with natural materials, add some minerals and trace elements, and vitalize the water while draining. This vitalization also happens in nature. You don't have this effect with most water filter systems offered.

When do you use a TDS meter?

Aquarium owners use the TDS meter to determine if the composition of the water is still good for the fish. As soon as an excess of certain substances occur in the water then they will have to take steps.